This invention relates to organo-soluble ethylhydroxyalkylmethylcellulose ethers.
Various cellulose ethers have been known and sold commercially for many years. These commercially available cellulose ethers are typically the reaction products of alkali cellulose with C.sub.1-4 alkyl chlorides, C.sub.2-4 alkylene oxides, chloroacetic acid and the like.
Most of the commercially available cellulose ethers such as methylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose and the like are employed as thickeners, protective colloids, film formers and for other uses in aqueous systems. While these cellulose ethers are useful in aqueous systems, the water-soluble ethers are generally insoluble in organic solvents and nonthermoplastics. Accordingly, these cellulose ethers cannot be employed in organic systems such as inks, and the like.
To meet the need for a cellulose ether with organic solubility, more hydrophobic cellulose derivatives such as ethylcellulose and ethylhydroxyethylcellulose have been developed. While these cellulose ethers are both organo-soluble and thermoplastic, said ethylcellulose and ethylhydroxyethylcellulose have other deficiencies which significantly limit their utility. For example, most ethylcellulose is not soluble in nonhydrogen bonded solvents, particularly those having low solubility parameters, such as C.sub.6 or higher alkanes, benzene, alkyl substituted aromatics, and the like. Generally, if solubility in such nonpolar solvents is required, ethylcellulose cannot be employed. Since recent price increases have made the use of these nonpolar solvents more economically attractive, the insolubility of ethylcellulose in these solvents is a significant limitation on their use.
Certain very highly substituted ethylcellulose and ethylhydroxyethylcellulose derivatives do have the desired solubility in such solvents, but are very difficult and expensive to prepare.
In addition, due to the conditions of their preparation, both ethylcellulose and ethylhydroxyethylcellulose are generally available only in relatively low molecular weight species. This limitation in molecular weight greatly reduces the utility of these cellulose ethers. Accordingly, an organo-soluble cellulose ether which can be prepared having high molecular weights would be highly desired.
Moreover, the preparation of ethylhydroxyethylcellulose is difficult and expensive from a production view point. The ethylene oxide used in the preparation of ethylhydroxyethylcellulose reacts with water, ethyl chloride and other impurities present in the reaction mixture. Consequently, the low overall yield of the process is greatly reduced and a variety of by-products are formed which are difficult to remove from the product.
Accordingly, a cellulose ether which is soluble in a wide variety of organic solvents and is thermoplastic would be highly desirable. Alternatively and additionally, an organo-soluble cellulose ether which may be prepared having high molecular weight and without the processing limitations of conventional organo-soluble ethers would be highly desired.